Mobile electronic devices are becoming more and more ubiquitous because they help users manage their busy schedules, as well as communicate with the world. For example, portable computers, such as notebook or laptop computers, personal data assistants (PDAs) and mobile telephones are becoming necessities for many. Notebook or laptop computers are very popular because they are extremely lightweight personal computers that can easily fit in a briefcase for the mobile businessperson. A PDA is a handheld mobile device that allows users to access information, keep track of their busy schedules, and communicate with others. A typical PDA can function as a mobile or cellular phone, fax sender, and personal organizer. Furthermore, many PDAs are capable of wireless connectivity. It is very important for today's mobile professional to be able to access information from anywhere in the world. Similar to the portable computer, PDAs are very popular because they are designed to be highly portable.
Positional systems have been recently incorporated into personal computers, electronic mobile devices and automobiles. For example, as described in U.S. Pat. No. 5,528,248 to Steiner et al., entitled “Personal Digital Location Assistant Including a Memory Cartridge, A GPS Smart Antenna and a Personal Computing Device”
Real time positional systems often access positional data from various sources, such as local transmitters or satellites. Real time positional systems include GPS (Global Position Satellites), MLS (Microwave Landing Systems), GSM (Global System Mobile), GIS (Geographical Information Systems) and CPS (Cambridge Positioning Systems).
A typical GPS unit includes (along with other components), a GPS receiver for receiving transmitted signals from a number of satellites, a memory in which cartographic data and other location information may be stored, a processor and associated GPS software for determining the location of the unit as a function of the received satellite signals and for accessing and processing data and information in the memory, and typically a display for displaying the information along with an indication of the unit's location. The memory may be integral with the processor, memory chips coupled with the processor, may include plug-in memory modules that fit within corresponding memory slots in the receiver or may be accessed remotely via a network such as wirelessly through the Internet. The processor retrieves information from the memory, for example, to display maps and routing instructions to permit a user of the GPS receiver to navigate to a desired location.
U.S. Pat. No. 6,778,837 to Bade et al. also incorporates GPS functionality into a PDA. Bade et al. describes a system and method for providing access to mobile devices based on positional data. The method involves predefining access parameters, determining the actual location of the device and automatically controlling access to the device.
Aside from size, the principal difference between a notebook, PDA or laptop computer and a personal computer is the display screen. Mobile devices typically use flat-panel technologies, which are lightweight and non-bulky. The primary function of a display screen is to provide a clear and readily viewable presentation to a user. One of the most important factors affecting a user's ability to easily perceive the shapes or images of a presentation is sufficient illumination of the display screen. Ambient light is often insufficient to provide adequate illumination of a display screen and a display screen usually includes lighting provisions such as a backlight. Since, providing too much backlight can also result in whiting out the screen, it is desirable to provide backlights that are automatically controlled.
U.S. Pat. No. 6,812,649 to Kim provides a device and method for controlling LCD backlight. Kim teaches a backlight control device and method for reducing or minimizing the battery usage. Kim teaches operating backlight control using intensity of detected surrounding light within a selected control range from a plurality of backlight control ranges. The backlight control ranges can vary in number but are directed into various levels, according to the intensity of surrounding light and use of a battery or an external power source.